A metal pipe has conventionally been used to suppress a decrease in vacuum degree in a vacuum chamber by degassing or gas permeation from a pipe when the interior and exterior of the vacuum chamber evacuated to a medium to high vacuum atmosphere are connected via the pipe and gas (or liquid) is supplied to or discharged from the interior/exterior of the vacuum chamber. A pipe for driving an alignment apparatus arranged in the vacuum chamber is generally a metal pipe having a flexible bellows structure in order to ensure the flexibility.
FIG. 12 is a schematic view showing an alignment apparatus arranged in a conventional vacuum chamber and its pipe. As shown in FIG. 12, an object 502 in a vacuum chamber 501 held in a high vacuum is precisely aligned by driving a stage 503 on a surface plate 504 by gas (or fluid). Since the stage 503 requires supply and discharge of fluid such as gas (or liquid), the interior and exterior of the vacuum chamber 501 communicate with each other via a flange 505 and metal pipes 506 having a bellows structure. An arrow shown above the stage 503 in FIG. 12 indicates the movable direction of the stage 503.
The use of the metal pipes connected to the alignment apparatus arranged in the vacuum chamber has the advantage that almost no degassing or gas permeation from the pipes occurs, but suffers from the following two serious problems.
(i) Because of low flexibility (high flexural rigidity), the load resistance of movement is high. In other words, a force in deforming the pipes acts as a disturbance factor to the stage 503, which adversely influence the alignment precision.
(ii) Repetitive deformation of the metal pipes 6 readily causes metal fatigue and decreases the durability.
In particular, the alignment precision of the high-precision stage 503 is adversely influenced by the nonlinear piping force of even a pipe made of a flexible resin material. For this reason, the low flexibility of the metal pipe poses a serious problem, and demands are arising for a flexible pipe usable in a vacuum chamber. The metal pipe may be replaced by a pipe made of a flexible resin material. In general, a resin material exhibits a larger amount of degassing or gas permeation than a metal pipe, so a resin pipe is difficult to directly use in a medium to high vacuum atmosphere.